No Subject

[js_dukelow@ccmail.pnl.gov]

I am puzzled by something that
Kent Lambert wrote to RADSAFE on 16 Feb 1996 (Digest 826):

> One should keep in mind that a microcurie of an electron emitter delivers
> a much smaller dose when it is in the body that it does when it is on the
> the skin.  And skin contamination is much more likely than an uptake.
> Therefore, the most critical concern has to be skin contamination.

I am assuming that by electron emitter, he is referring to both radionuclides 
that undergo beta decay and those that undergo internal conversion and eject 
an electron of a particular fixed energy from the electron shells around the 
atom.

My first thought on reading this was that half of the betas in a skin 
contamination fly off in the other direction and waste their sweetness on 
the desert air.  Internally-deposited beta-emitters, on the other hand, 
will deposit virtually all of their energy inside the body and, more 
particularly, in the organs or tissues that they settle in.  I recognize 
that skin contamination may cause very high local doses to the squamous 
layer of the skin.  At the same time, low- to mid-energy betas will 
deposit a significant fraction of their energy in the outer layer of dead 
skin cells. 

Secondly, skin contaminations are more likely to be detected, are more 
easily mitigated, and in the event that they lead to cancer, that cancer 
announces itself earlier and is more likely to be curable than a cancer 
resulting from internal deposition.  I would be much more concerned about 
an internal deposition of a beta- or electron-emitter. 

Am I missing something here?

Best regards.

Jim Dukelow
Pacific Northwest National Laboratory
Richland, WA

js_dukelow@pnl.gov
These are my own thoughts and have not been reviewed and/or approved by my 
management or the Department of Energy.